1. Field of the Invention
The present invention relates to elevators, and more particularly, to an elevator safety apparatus that can prevent the elevator from uncontrolled descent when, for instance, the cord pulling the elevator breaks off or the motor stalls.
2. Description of Prior Art
A prior art elevator safety apparatus is disclosed in ROC Application No. 6,926,655, which is shown in FIGS. 5-6. In this prior art elevator safety apparatus, steel core 1 supports the hanging structure 3 through pulley 2. The opposite ends of the hanging structure 3 are inserted into securing frames 5 which allow the hanging structure 3 to be movable along the vertical direction. A pair of grooved plates 6 extend from two sides of the hanging structure 3. A pressing member 7 is provided at the outer end of the grooved plate 6. A pair of securing rods 8 is sleeved with spring 9, with its two ends passing through the grooved plate 6 and secured to the top of the elevator 4. In normal conditions, since the elevator 4 is suspended by the steel cord 1, the spring 9 is depressed by gravitational pull. In emergency conditions when the steel cord 1 breaks off, the elastic force from the spring 9 presses the grooved plate 6 and the pressing member 7 and hanging structure 3 down against the top of the elevator 4. The stopping device B is mounted on the grooved plates 10 and attached to guiding posts 11. The grooved plate 10 and the angled iron plate 12 constitute a mount for a braking member 13. A threaded bar 15 is engaged with a threaded hole 14a. A ball 16 is inset at the head of the threaded bar 15, which presses against a pushing member 17. The top and bottom of the pushing member 17 are each provided with a cylindrical member 18. The other end of the cylindrical body is inserted at the back of the braking member 13. A linkage arm 19 is provided with its center pivoted at the rear end of the threaded bar 15. Its upper portion is coupled to the bottom of the pressing member 17 via pulleys and its lower portion is coupled to the linkage bar 20. The elevator safety apparatuses B, B', and B" are all identical in structure. One end of the linkage arm 21 is connected to the outer end of the threaded bar on the elevator safety apparatus B' and the other end connected to the linkage bar 20. The elevator safety apparatus B" is also connected to the linkage bar via the linkage arm 22. When the linkage arms 19, 21, 22 are pushed in a specific direction, the threaded bar 15 on each elevator safety apparatus B, B' and B" screws forward into the box 14. Concurrently, the pushing member 17, the cylindrical member 18, and the braking member 13 move toward the guiding post 11. This causes friction between the braking member 13 and the guiding post 11.
In an emergency condition when the cord pulling the elevator breaks off, the pressure exerted to the spring 9 disappears such that the elasticity of the spring 9 forces the pressing member 7 to press down against the underlying linkage arm 19 which in turn transmits the pressure to the linkage arms 21, 22 via the linkage bar 20 at the other end, causing the braking devices B, B' and B" to operate and thereby stopping the elevator 4.
It is a drawback of the aforementioned prior art that constituent parts of the braking devices B, B', and B" and those of the transmission mechanism from the pulley 2 to the braking devices B, B', and B" are so numerous that the structure is quite complex. This makes the prior art elevator safety apparatus slow in action, liable to easy malfunction, and hard to maintain.
In the prior art elevator safety apparatus, the elevator's motor is not switched off when the elevator is stopped in emergency conditions. This usually causes the circuit of the motor to break down and can thus cause fire.
In addition, there exists a need for a beeper that can produce an alarm or SOS call to the outside when the elevator is in an emergency situation.